1. Field of the Invention
This invention generally relates to a method and apparatus for determining the distribution of light or the direction of a light beam irradiated from a lamp, and, in particular, to a method and apparatus for determining the light distribution or irradiation direction of a light beam emitted from a headlight of an automobile or the like.
2. Description of the Prior Art
In determining the irradiation distribution of a light beam emitted from an automobile headlight, it is common practice to have the light beam directed toward a screen which is placed in front of the headlight approximately 3 meters away and to look for a maximum light intensity point visually. Alternatively, a pair of photoelectric sensors are provided on the screen so as to be movable in the vertical direction and another pair of photoelectric sensors are also provided on the screen so as to be movable in the horizontal direction, wherein the sensors are located such that the outputs from the paired sensors are balanced thereby determining a light axis of the beam. Then, the mounting condition of headlight is adjusted such that the thus determined light axis corresponds to an intended irradiation direction.
However, these prior art approaches suffer from various disadvantages because the light intensity distribution of a light beam from an automobile headlight could be quite irregular thereby making it difficult to definitely determine the maximum light intensity point and equi-irradiation curves are often times distributed not in a concentric manner, whereby the maximum light intensity point is located eccentrically or there exists more than one. Thus, there has been a need to develop an improved method and apparatus for determining more accurately the distribution of irradiation or irradiation direction of a light beam emitted from an automobile headlight.